1. Field of the Invention
This invention relates to a focus detecting device used in a still cameras, etc. and in particular, to the assembly adjusting mechanism thereof.
2. Related Background Art
A focus detecting device in which the object light having passed through a photo-taking lens is directed onto a photoelectric conversion element through a focus detecting optical system and the focus adjusted state of the lens is detected on the basis of the output of the photoelectric conversion element is well known. This focus detecting optical system comprises, for example, a field lens disposed near the predetermined focal plane of the photo-taking lens, two imaging lenses disposed rearwardly thereof, etc., and a line sensor, comprising a photoelectric conversion element, disposed rearwardly of the optical system. Focus detection is accomplished by finding the correlation between two images formed on the line sensor by the two imaging lenses.
Now, the units such as the field lens and the imaging lenses are usually fixedly fitted to a unit body for focus detection, and the mutual adjustment of those units is little known. For example, Japanese Laid-Open Patent Application No. 39612/1985 discloses a technique whereby when effecting pupil adjustment or the like, each unit is not moved but the unit body is moved as a unit. However, the secondary imaging lens, the field lens, etc. are fixedly fitted to the unit body, and each unit has little freedom for adjustment. Nevertheless, each unit is not always appropriately fixed to the unit body including a sensor, and for example, the following problem arises in some cases.
FIG. 10 of the accompanying drawings shows the images formed on the sensor. Reference characters 31a and 31b designate a pair of sensor portions, and reference characters 30a and 30b denote projected images. When the sensor or the secondary imaging system is somewhat rotated as shown, different portions of an object to be photographed are distance-measured, and this cannot be an said to be accurate distance measurement, and the adjustment thereof becomes impossible. That is, an attempt to fixedly fit and dispose each unit at an appropriate location would require accuracy of the design or manufacture thereof.
U.S. Pat. No. 4,391,513 is mentioned as a known art.